Biscuit expert? (4)
I believe the answer is:
buff
I believe this clue is a double definition.
'biscuit' is the first definition.
(both can mean a brown colour)
'expert?' is the second definition.
(buff can mean an expert or aficionado)
(Other definitions for buff that I've seen before include "Polish; muscular" , "Dull brownish-yellow - expert" , "Polish; yellow-beige" , "excellent muscle tone" , "Yellowish-beige; expert" .)